Monday, August 28, 2006

Spyce will not waste your time: controllers/handlers

Traditional view-oriented frameworks (such as PHP, or Spyce 1.3) do not handle control logic well. Today I'll show how Spyce 2 solves this problem with "active handlers," and tomorrow I'll show how this lets Spyce provide much more elegant code-reuse tools than either other view-oriented frameworks or MVC frameworks like Turbogears and Django.
Control logic is the code that decides what happens next in response to a user action. Say we have a simple form to create new to-do lists, like this:

This takes care of the redundant code to access form variables -- Spyce inspects the function definition and pulls the corresponding values out of the request for you -- and it also solves the problem of how to organize your code.
Earlier, I said you could write "handler=list_new." Actually, you either need to write "handler=self.list_new" and define list_new in a class chunk in the current page (as demonstrated in this example), or you can write "handler=somemodule.list_new," and put list_new in somemodule. (In the spirit of Not Wasting Your Time, Spyce will take care of importing somemodule as necessary.)
Pretty simple stuff, but I needed to explain handlers before I get into how Spyce uses them with active tags to provide unique code re-use tools. That will be our topic next time! Until then, if you missed the entry on form processing, go read it, since it touches on some of the more advanced features of handlers.